Figure 8 RIGHT.
Photograph of the outcrop showing the thin sandstone layers.
If bioturbation of the sandstone did occur as Sheehan (1988)
has suggested, then the sandstones should have been obliterated
by bioturbation, especially the thin layers. However, if the
sands were deposited in turbidity currents with the clays serving
as the trace maker substrate, then the sandstones would serve
as sole casts and would reflect the bioturbated nature of the
clays. With eventual sedimentary loading and tectonic input,
the clays would be compressed into the shale layers seen today,
and all that would remain as evidence for trace maker activity
would be preserved as sole casts along the bottoms of the sandstone
layers. The sandstone trace maker cast is what is found along
the bottom of even the thinnest sandstone layers.